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microgreen growing soil coco coir pouring from a cup into a microgreen tray
August 26, 2022

The Best Soil for Microgreens

Microgreens require light, porous, clean soil.

The best growing medium for microgreens is coco coir

Seed germination and microgreen nutrition start with the right growing medium. It is important to have a soil with good physical characteristics. It must have a high air and water-holding capacity, as well as one that is pathogen-free. Microgreens are grown in high-density conditions. With many roots in a small space so it is vital that the soil have the ability to retain both air and moisture to allow the roots to grow quickly. Because we eat a product that is harvested a half-inch from the soil, the soil must also be pathogen-free to protect health.

Coco coir comes from the outside part of the coconut. Think of a coconut like a peach. In the peach, we eat the ‘flesh’ and throw away the seed. With a coconut, however, we eat the ‘seed’ and throw away the flesh. As the coconut is harvested the outer part, the husk, is cut off and discarded by the nut growers. It is this part that is turned into coco coir. Designed by nature to give the right nutrients to a growing seed (the coconut), it has exactly what microgreens need.

Coir gives us ease of use, zero waste, ecological sustainability, and little to no cleanup. No dirt in the house!

Soils that are heavy, such as garden soils, retain too much water.

Waterlogged soil surrounding a plant’s roots robs the roots of the oxygen they need to grow. It also gives just the right conditions for mold growth as well as damping off problems. The ideal soil retains enough moisture to provide just the right amount of constant moisture, as well as porous enough to retain oxygen to give the roots optimal growing conditions. Although garden soil may grow magnificent outdoor gardens, it lacks the drainage, aeration, and moisture control necessary to successfully grow microgreens.

Be wary of potting mixes

Potting mixes have a lot going for them- they do a good job of holding both air and water, easy to find, and grow microgreens quite well. So why is it not the preferred growing medium? Because of the potting mix’s “dark side”. Most potting mixes are made up of peat moss, decomposed bark, and perlite. Peat moss is not a renewable resource- at least not in a human time frame. Growing just a millimeter per year, when we purchase peat moss we are buying a resource that grew for thousands of years.

The second issue is the source of the bark or other organic material. Much is sourced from landfills. While this is a great way to recycle, there is no way to know what was on the organic matter that goes into the landfills. That is not a problem when growing flowers, but when we are growing food that is harvested so close to the soil, we must be assured that there are no wayward chemicals in the soil. Use potting mixes for flowers, but stick to coir for microgreens.

Microgreens do not require fertilizer

Microgreens are harvested during the cotyledon stage- before the true leaves come out. During this period of growth, it is the breakdown of the starch in the seeds, the breakdown of phytate (which inhibits the absorption of nutrients in the body) as well as photosynthesis that is responsible for the massive increase of nutrients from seed to microgreen. Adding nutrients to the soil or water while growing to microgreen size is unnecessary and counter-productive.

No need for expensive mixes or supplements

Organic, triple-washed coconut coir gives stability to the growing seeds, as well as a constant supply of just the right amount of moisture and nutrients. It requires watering infrequently for ease of use, and it is organic and pathogen-free for safety.

A little more about coir: turning coconuts into coco coir

Coir has many uses, from gardening and soil erosion to ropes and fishing nets to upholstery and packaging materials. The destined use often determines how it is handled from grower to manufacturer.

To make the raw coir from the coconuts into the perfect substrate for microgreens, the coir must be combed, the natural salt eliminated by multiple washings, and the large fibers removed.

Coir that is prepared specifically for microgreens is grown organically, is triple-washed for salt removal, the large fibers combed out, and the resulting finer fiber is then pulverized and compacted, and cut to just the right size to make discs that almost instantly rehydrate to the exact amount needed for each 5×5 tray. This eliminates the need to rehydrate large blocks that have to then be re-dried over many days or weeks and stored in huge bins. It also prevents the possibility of contamination that can occur when rehydrating and storing large blocks.

Our coco coir discs are prepared specifically for us

Coconuts are not grown in the US, so we source ours from a family-owned organic producer in India, where most coco coir is grown and processed. They prepare the coir to our specifications (fine comb, triple washed, salt free and the exact size we require). The factory is run by women who not only earn a living, but care about what they are doing.

Organic Coir Discs are included in all of our kits

We include our organic coir discs in all of our kits. This makes growing microgreens simple for all ages. Add a disc to 1/2 cup water, watch it rapidly expand, then dump it into the tray. If there are children in the house, encourage them to participate. Watching the coir increase from a small disc to a cup of soil is always guaranteed to get a “Whoa! Look at that!”

Choose your coir here

2 comments on “The Best Soil for Microgreens”

  1. Thank you for your insight. I found that Coco Coir works extremely well! It is definitely more reliable when taking possible disease or mold into account. I have found though that a good batch from a potting mix is much greener and crunchier than a good batch from Coco Choir. Why is that if microgreens don’t require fertilizer?

    1. Hello Rei, thank you for your question! Seeds were ‘designed’ to grow in soil- and normally the richer the soil, the bigger the plant grows. This holds true with microgreens to a lesser extent mainly because we are harvesting right before the plants require additional nutrients to explode into quick growth. There have been only a few studies done comparing the nutrients when grown in potting mix and coir, and each one shows negligible differences in nutrients. is one such small study. I believe that adding fertilizer is possible and will not harm, but since it is the nutrients in the microgreens that we are after with as little effort as possible, the coir still gives the medium that is most suitable for home/family growing.

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